An oil or gas well typically comprises a hole, called a well bore, which is drilled from the earth's surface or the sea floor to a level containing oil or gas. The well bore is frequently lined with pipes referred to as casing which reinforce the well bore. The casing in turn surrounds further pipes, referred to as production pipe, which is used to carry oil from inside the well bore to the earth's surface.
At various stages during drilling, completion, and/or workover of a well, there is a need to clean out the well bore and/or the production pipe. For example, after drilling, cementing, or perforating operations, a large amount of particulate matter removed from the sides of the well bore during these operations remains at the bottom of the well bore. Furthermore, during pumping operation of a well, sand and other particles may accumulate inside the production pipe and may partially or completely block fluid flow through the production pipe, thereby decreasing the efficiency of the well. Since the blockage may be thousands of feet beneath the earth, it is often uneconomical to pull the production pipe up to the surface to remove the blockage. Accordingly, there is a need for a method which can efficiently clean out an oil or gas well to remove particles from the bottom of the well bore and remove blockages of the production pipe without having to pull the production pipe out of the well.